Hitherto, when carrying out operation of instruction to an industrial robot, an operator grips or grasps a portable controller by one hand or both hands to push a key or keys on the controller by thumbs of the both hands or finger of hand by which the controller is not gripped (held). In the portable controller, so called a deadman (dead-man's type) switch such that it is operative for a time period during which the controller is touched by hand, and it is stopped when hand is away from the controller is assembled in view of safety in the operation of the robot. As a portable controller of this type, there is disclosed a portable controller in which, in order that respective finger tips come into contact with keys of the controller at the same time when the operator grips or holds the portable controller from the lateral direction, a pressing plate of the deadman switch is disposed at the back side of the portable controller, and an inclined surface is provided at the controller back side edge portion with which hand of the operator comes into contact (e.g., Japanese Patent Application Laid Open No. 207580/1988).
Moreover, there is disclosed a portable controller in which a finger fitting portion having a shape such that finger is fitted is provided on the back side of the portable controller in order that an operator dose not become tired even if he grips or holds it for a long time (e.g., Japanese Utility Model Application Laid Open No. 70893/1988).
Since the work for giving instruction to the robot is carried out near the robot body, it is necessary to imergently or immediately stop the robot for the purpose of protection of the operator when the robot runs away for any reason. As a momentary operation when the robot runs away, there are instances where the operator allows his hand to be away from the portable controller, or there are instances where he tightly grips or grasps the portable controller.
However, in the constitution in which the deadman switch which is stopped when operator's hand is away from the controller is assembled as described above, there was the drawback that when operator tightly grips the controller, its objective is not attained although there is the effect when operator's hand is away from the portable controller.